Flexible surgical devices

ABSTRACT

A surgical device can include a tube comprising a wall having a plurality of slits oriented generally transverse to a longitudinal axis of the tube. Each of the slits may be defined by opposing surfaces. The surgical device can further include a force transmission element coupled to the tube. In a flexible state of the tube, at least some of the opposing surfaces defining respective slits are separated from one another, and in a stiffened state of the tube, a force exerted on the force transmission element causes the opposing surfaces of each slit to contact one another.

TECHNICAL FIELD

The present teachings relate generally to flexible surgical devices.More particularly, the present teachings relate to flexible surgicaldevices that can be varied between flexible and stiffened states forminimally invasive surgery.

BACKGROUND

Minimally invasive surgical techniques generally attempt to performsurgical procedures while minimizing damage to healthy tissue. Oneparticular technique for achieving this goal employs flexible surgicaldevices that are able to reach a target work site inside a patient by atleast partially following a natural lumen, such as, for example, thedigestive tract, blood-carrying lumens, or other lumens, of the patient.Following a natural lumen, for example, can allow a surgeon to operateat a work site while making fewer and/or smaller incisions throughhealthy tissue, although an incision may be needed at locations wherethe flexible device enters or leaves a natural lumen.

Surgical devices that are able to follow a natural lumen or othertortuous paths must therefore be flexible, which requires the devices tohave properties and abilities that may not exist or be needed in othersurgical instruments. Furthermore, although a surgical device must beflexible enough to navigate a tortuous path, in order to properlymanipulate a surgical tool (e.g., an end effector) positioned at adistal end of the device, the surgical device must also provide a stablebase once positioned at a work site.

In certain surgical applications and devices, however, a rigid minimallyinvasive instrument may be more effective for carrying out variousprocedures. Such instruments' inherent stiffness may be useful for taskssuch as retraction, dissection, and suture tightening because a flexibledevice, even if prevented from bending by holding its actuatingmechanisms stationary, is less stiff than a rigid instrument of similarouter diameter. As another example, if two minimally invasiveinstruments are used at an internal surgical work site, it is oftendesirable to have these instruments angled to one another so as toprovide a triangulation that allows a surgeon to view the work site(e.g., using an endoscope) without the instruments blocking the view. Inaddition, such instrument triangulation often provides a more effectiveconfiguration for various surgical tasks (e.g., dissection, suturing,knot tying, etc.) than instruments that are oriented relatively parallelto one another.

Some conventional surgical devices that are actuatable between flexibleand stiffened states have interconnected articulating links in a varietyof arrangements to provide bending in one and/or multiple degrees offreedom (DOF) when in a flexible state. Such devices generally alsoinclude a force transmission mechanism (e.g., tension elements)interconnected to the links to control the bending of the device in theflexible state and to place the device in the stiffened or flexiblestate. Other devices may use other methods of rigidizing an instrument.For example, U.S. Patent Application Publication No. US 2009/0299343 A1(filed May 25, 2008; entitled “Stiffening Assembly”) discloses leafstructures that may be compressed to stiffen a flexible structure. Asanother example, U.S. Patent Application Publication No. US 2008/0091170A1 (filed Jun. 30, 2006; entitled “Canula System for Free SpaceNavigation and Method of Use”) discloses stiffening embodiments thatinclude thermal, vacuum, and pressure stiffening methods, as well astension element rigidizing methods. Yet another example is U.S. PatentApplication No. US 2010/0160724 A1 (filed Dec. 23, 2008; entitled“Flexible Surgical Instrument with Links Undergoing Solid-StateTransitions”), which discloses a long link made of a shape memory alloyor another material having one state in which the link is sufficientlyflexible to bend as needed to pass through a curved entry guide andanother state in which the link returns to a desired shape and issufficiently rigid for precise controlled movement. Since thesestructures have a relatively large number of different parts, the costsassociated with manufacturing and assembling these parts can berelatively high. Thus, flexible minimally invasive surgical instrumentshave certain advantages over rigid straight or curved minimally invasivesurgical instruments, and vice-versa. Likewise, both instrument typeshave certain disadvantages in both use and construction. It isdesirable, therefore, to have a single minimally invasive surgicalinstrument that includes the benefits of both flexible and rigidinstruments while at the same time minimizing their effectivedisadvantages.

To navigate tight, tortuous paths and perform complex motions (e.g., ata surgical work site), it may therefore be desirable to provide asurgical device that is sufficiently flexible to follow a variouslycurved path in a flexible state, while also providing sufficientrigidity in a stiffened state. It may also be desirable to provide asurgical device that can transition between flexible and stiffenedstates, using, for example, existing actuation systems and controls.Further, it may be desirable to provide a surgical device that cantransition between flexible and stiffened states, can be made ofrelatively simple structures, can reduce the number of components and/ordifferently configured components, and/or can provide for relativelyrobust manufacturing.

SUMMARY

The present teachings may solve one or more of the above-mentionedproblems and/or may demonstrate one or more of the above-mentioneddesirable features. Other features and/or advantages may become apparentfrom the description that follows.

In accordance with various exemplary embodiments of the presentteachings, a surgical device can include a tube comprising a wall havinga plurality of slits oriented generally transverse to a longitudinalaxis of the tube. Each of the slits may be defined by opposing surfaces.The surgical device can further include a force transmission elementcoupled to the tube. In a flexible state of the tube, at least some ofthe opposing surfaces defining respective slits are separated from oneanother, and in a stiffened state of the tube, a force exerted on theforce transmission element causes the opposing surfaces of each slit tocontact one another.

In accordance with various additional exemplary embodiments of thepresent teachings, a method can include longitudinally compressing asurgical instrument tube when a command to place the tube in a stiffenedstate is received. Longitudinally compressing the surgical instrumenttube causes opposing surfaces of slits in the tube to contact oneanother. The method can further include reducing the longitudinalcompression on the surgical instrument tube when a command to place thetube in a flexible state is received, and reducing the longitudinalcompression allows the opposing surfaces of at least some of the slitsto be separated from one another.

Additional objects and advantages will be set forth in part in thedescription which follows, and in part will be obvious from thedescription, or may be learned by practice of the present teachings. Theobjects and advantages may be realized and attained by means of theelements and combinations particularly pointed out in the appendedclaims and their equivalents.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present teachings can be understood from the following detaileddescription either alone or together with the accompanying drawings. Thedrawings are included to provide a further understanding of the presentteachings, and are incorporated in and constitute a part of thisspecification. The drawings illustrate one or more embodiments of thepresent teachings and together with the description serve to explaincertain principles and operation.

FIG. 1 is a schematic view of an exemplary embodiment of a surgicaldevice in accordance with the prior art;

FIG. 2 is a side elevation view of one exemplary embodiment of thedistal portion of a surgical device in accordance with the prior art;

FIG. 3 is a schematic view of an exemplary embodiment of a surgicaldevice in accordance with the present teachings;

FIG. 3A is a side elevation view of a distal portion of FIG. 3;

FIG. 3B is a partial perspective view of the tube of FIG. 3;

FIG. 4 is a schematic view of the tube of FIG. 3 illustrating tensionelements in accordance with the present teachings;

FIG. 5A is a diagrammatic view of the tube of FIG. 3 in a flexiblestate;

FIG. 5B is a partial perspective view of the tube of FIG. 3 in a flexed(bent) state;

FIG. 5C is a partial perspective view of the tube of FIG. 3 in astiffened state;

FIG. 5D is a diagrammatic view of the tube of FIG. 3 in a stiffenedstate;

FIG. 5E illustrates a partial diagrammatic view of a tube in accordancewith various additional embodiments of the present teachings;

FIG. 5F illustrates another partial diagrammatic view of a tube inaccordance with various additional embodiments of the present teachings;

FIG. 6 is a schematic view of an actuation mechanism in accordance withthe present teachings;

FIG. 7 is a partial side elevation view of an exemplary embodiment of asurgical system in accordance with the present teachings;

FIG. 8 is a partial side elevation view of an exemplary embodiment of asurgical system;

FIG. 9 is a schematic view of another surgical device in accordance withthe present teachings;

FIG. 10 is a partial elevation view of the tube of FIG. 9;

FIG. 11 is a partial cross-sectional schematic view of the tube of FIG.9 illustrating tension elements in accordance with the presentteachings;

FIGS. 11A-11C are the respective cross-sectional views taken from11A-11A, 11B-11B, and 11C-11C of FIG. 11;

FIG. 12 is a flow diagram of a method for altering a surgical devicebetween stiffened and flexible states in accordance with an exemplaryembodiment of the present teachings;

FIG. 13 is a flow diagram for actively controlling the configuration ofthe surgical device in accordance with the method of FIG. 12;

FIG. 14A is a partial cross-sectional view of yet another exemplaryembodiment of a tube illustrating compression elements in accordancewith the present teachings; and

FIGS. 14B and 14C show schematic views of opposing surfaces of a slit onan inner bend radius of the tube of FIG. 14A in response to variousbending forces applied to the tube.

DETAILED DESCRIPTION

This description and the accompanying drawings that illustrate exemplaryembodiments should not be taken as limiting and the claims define thescope of the present teachings. Various mechanical, compositional,structural, electrical, and operational changes may be made withoutdeparting from the scope of this description and the invention asclaimed, including equivalents. In some instances, well-knownstructures, and techniques have not been shown or described in detail soas not to obscure the disclosure. Like numbers in two or more figuresrepresent the same or similar elements. Furthermore, elements and theirassociated aspects that are described in detail with reference to oneembodiment may, whenever practical, be included in other embodiments inwhich they are not specifically shown or described. For example, if anelement is described in detail with reference to one embodiment and isnot described with reference to a second embodiment, the element maynevertheless be claimed as included in the second embodiment.

For the purposes of this specification and appended claims, unlessotherwise indicated, all numbers expressing quantities, percentages, orproportions, and other numerical values used in the specification andclaims, are to be understood as being modified in all instances by theterm “about.” Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the following specification andattached claims are approximations that may vary depending upon thedesired properties sought to be obtained by the present invention. Atthe very least, and not as an attempt to limit the application of thedoctrine of equivalents to the scope of the claims, each numericalparameter should at least be construed in light of the number ofreported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Moreover, all ranges disclosed hereinare to be understood to encompass any and all subranges subsumedtherein.

It is noted that, as used in this specification and the appended claims,the singular forms “a,” “an,” and “the,” and any singular use of anyword, include plural referents unless expressly and unequivocallylimited to one referent. As used herein, the term “include” and itsgrammatical variants are intended to be non-limiting, such thatrecitation of items in a list is not to the exclusion of other likeitems that can be substituted or added to the listed items.

Some conventional surgical devices, including articulated arms andstructures used to support and move surgical tools, are eithersubstantially flexible or rigid, while other surgical devices aretransitioned between flexible and rigid states. For minimally invasivesurgery, it may be desirable for a surgical device to achieve both aflexible state and a stiffened state. Accordingly, exemplary embodimentsof the present teachings consider surgical devices that can be alteredbetween a flexible state and a stiffened state. These devices include,for example, a tube that has a plurality of slits along at least aportion of the tube, for example, slits through the tube wall.

In various exemplary embodiments, the slitted tube may be interconnectedwith other structures, such as, for example rigid link structures, toform the articulable surgical device. In other exemplary embodiments,the slitted tube may be used alone, for example, in place of one or moreconventional articulable serial link structures. Thus, exemplarysurgical devices may include, for example: (i) arms that have a seriesof two or more passive, flexible tubes connected by joints having atleast one DOF, and (ii) active, continuously flexible tubes having atleast one DOF that can be used alone to replace an articulating seriallink structure (i.e., the tube itself can form the articulating arm). Asthose of ordinary skill in the art would understand, however, theembodiments as described generally above and in detail below areexemplary only and not intended to be limiting of the present teachingsor claims. Surgical devices in accordance with the present teachingsmay, for example, also include hybrid structures, which include at leastone passive, flexible tube portion and at least one active, continuouslyflexible tube portion. Moreover, flexible slitted tubes in accordancewith various exemplary embodiments may be altered between passive andactive states, for example, via control systems that adjust the tensionin tension mechanisms associated with the tubes.

Exemplary embodiments described herein include various minimallyinvasive surgical devices, which may, for example, be used inconjunction with various robotic surgical systems. Robotic surgicalsystems are known, and examples of certain telerobotic surgical featuresand components may be found in systems such as the da Vinci® SurgicalSystem (specifically, a Model IS3000, marketed as the da Vinci® Si™ HD™Surgical System), commercialized by Intuitive Surgical, Inc. ofSunnyvale, Calif.

As used herein, the term “flexible” and variations thereof inassociation with a mechanical structure, such as, for example, a tube,should be broadly construed. The term describes structures (e.g., atube) that can be repeatedly bent and restored to its original shapewithout permanent deformation and/or other harm to the structure. Asthose of ordinary skill in the art would understand, many “rigid”structures have a slight inherent resilient “bendiness” due to materialproperties, although such structures are not considered “flexible” asthe term is used herein. As those of ordinary skill in the art wouldfurther understand, a structure's flexibility may also be expressed interms of its stiffness. Those ordinarily skilled in the art wouldappreciate that devices having a flexible state and a stiffened stateare in differing relative states of flexibility (or rigidity). Forexample, the flexible state may provide a degree of bending to thedevice that is significantly greater than when the device is in thestiffened state, in which the device acts more like a single, rigidstructure.

In accordance with the present teachings, a tube may also be eitheractively or passively flexible. An actively flexible tube may be bent byusing forces originating from sources associated with the tube itself,such forces acting on the tube to intentionally bend it (e.g., in anamount and direction) as desired. For example, one or more forcetransmission elements may be routed lengthwise along the tube and offsetfrom the tube's center longitudinal axis, so that a force on one or moreof the force transmission elements acts on the tube to cause the tube tobend. Exemplary force transmission elements that can be utilized to bendan actively flexible tube can include but are not limited to, forexample, tension elements that transmit a force on the tube when atension force is exerted on the elements (e.g., cables, filaments,wires, rods, etc.) and/or compression elements that transmit a force onthe tube when a compressive force is exerted on the elements (e.g.,rods). In either case, the force transmission elements should also besufficiently flexible in order to be able to bend as the tube bends, butstill enable a force to be transmitted to the tube to bend and/orstiffen the tube. A passively flexible tube is bent by a force externalto the tube and its associated components. For example, during aminimally invasive procedure, an external force may be the reactiveforce the tube experiences when pushed against tissue. As those ofordinary skill in the art would understand, however, an activelyflexible tube, when not actuated by its associated sources of force, maybe passively flexible. Furthermore, a tube may include one or moreactively and passively flexible portions in series.

As used herein, the term “a flexible state” refers to a state in whichthe tube's flexible nature is being used. In other words, when “in theflexible state” a tube is either actively or passively bendable or bent.For example, tension in one or more tension elements may cause the tubeto bend (i.e., while tension on the remaining tension elements isrelaxed), or a force external to the tube may cause the tube to bendwhen tension on one or more tension elements is relaxed (i.e., whentension on all the tension elements is relaxed).

As used herein, the term “a stiffened state” refers to a state in whichthe tube is actively rigidized. In other words, when “in the stiffenedstate” a tube is effectively rigid so as to be substantially preventedfrom passive bending of the tube. For example, a force may be exerted tosubstantially uniformly compress the tube along its longitudinal axis tothereby stiffen the tube (i.e., to provide sufficient rigidity for astable base). In exemplary embodiments, the compression force on thetube may be exerted by applying equal tension on one or more tensionelements associated with the tube. Thus, in the stiffened state, thetube is stiff enough so that it can be effectively controlled as asingle, rigid piece.

FIG. 1 schematically illustrates a side elevation view of an exemplarysurgical device 100. Surgical device 100 includes, for example, a seriallink structure (i.e., an arm) comprising a series of segments 102, 104,and 106 interconnected by joints 103 and 105. As depicted, a surgicalend effector 110 (e.g., grasper, needle driver, shears, cautery tool,camera, and/or the like) is coupled to the distal end of segment 106. Asillustrated and described in greater detail below, the surgical device100 may be actuated via cables 131 and 132 by an actuation mechanism130. In one exemplary embodiment, the segments 102, 104, and 106 can berigid links.

Although various structures can be used to form the surgical device 100,FIG. 2 shows a side elevation view of one exemplary embodiment of themechanical distal portion 250 of a surgical device, such as disclosed,for example, in U.S. Application Publication No. US 2008/0065102 A1(filed Jun. 13, 2007; entitled “Surgical Instrument with Parallel MotionMechanism”), the entire contents of which are incorporated by referenceherein. As shown in FIG. 2, the surgical device distal portion 250 caninclude illustrative joints 203 and 205 that each has two hingespivotable around orthogonal axes. The joints 203 and 205 areinterconnected by a rigid link 204, which can be in the form of a rigidtube. Thus, by providing differing pivoting arrangements in joints 203and 205, various shapes can be achieved over the distal portion 250 ofthe surgical device to achieve one or more of pitch and yaw movement ofthe arm to perform complex motions that can be desirable for varioussurgical tasks, examples of which include but are not limited to knottying, resection, suturing, etc. Permitting such complex motions canalso be useful in traversing tortuous paths and accurately reaching atarget site in a patient's body. Reference is made to U.S. ApplicationPublication No. US 2008/0065102 for various arrangements to achievevarious bending patterns in the arm.

Those of ordinary skill in the art would understand, however, thatsurgical device distal portion 250 is exemplary only and illustrates oneexemplary configuration for the surgical device 100 that is representedschematically in FIG. 1. The arrangement of elements shown in FIGS. 1and 2 is not intended to be limiting of the present teachings andclaims, but rather, as explained in more detail below, depict exemplarysurgical devices with which embodiments in accordance with the presentteachings can be utilized. Surgical device 100 may therefore comprisevarious types, numbers, and/or configurations of components (e.g.,interconnected joints, links, etc.) depending upon the particularsurgical application desired. In various embodiments, for example,joints 103 and 105 may function as a multi-link section (e.g., asindependently controlled joints), whereas in various additionalembodiments joints 103 and 105 may function as a pivoting joint pair(e.g., as mechanically coupled joints). Reference is also made to U.S.patent application Ser. No. 12/945,734 (filed Nov. 12, 2010; entitled“Tension Control in Actuation of Multi-Joint Medical Instruments”, andU.S. patent application Ser. No. 12/618,608, (filed Nov. 13, 2009;entitled “Curved Cannula Instrument”), the entire contents of both ofwhich are incorporated by reference herein, for various types andconfigurations of devices suitable for application of the flexible tubesof the present teachings.

Passively Flexible Surgical Devices

In accordance with aspects of the present teachings, a passivelyflexible, stiffenable tube is made by placing a large number ofrelatively thin slits in the tube wall across a width of the tube. Theseslits allow the tube to be flexible, and accordingly the widths of thevarious slits in the tube wall increase or decrease as the tube bends.To place the tube in a stiffened state, the tube is longitudinallycompressed, which closes the slits so that opposing surfaces of eachslit are pressed against each other. In this stiffened state, the tubeeffectively functions as an uncut (e.g., solid wall) tube. When thelongitudinal compression is relaxed (e.g., reduced or removed), the tubereturns to a flexible state, in which the opposing surfaces of each slitare spaced apart from each other. These aspects are discussed in furtherdetail below.

Referring now to FIG. 3, in accordance with various exemplaryembodiments of the present teachings, a surgical device 300 can compriseat least one passive, flexible segment, such as a passive, flexible tube304 having a plurality of slits 321 in the tube wall, as shown in moredetail in FIGS. 3A and 3B. Surgical device 300 includes, for example, aserial link structure (i.e., an arm) comprising a series of segments302, 304, and 306 interconnected by joint pairs 303 and 305. In variousexemplary embodiments, a surgical end effector 310 (e.g., grasper,needle driver, shears, cautery tool, camera, and the like) is coupled tothe distal end of segment 306. By way of example, therefore, the rigidlink 204 in the embodiment of FIG. 2 can be replaced with the passive,flexible tube 304 to provide an arrangement that can offer variousdesirable features, as described further below.

As used herein the term “tube” refers to structures that are generallyhollow and can pass and/or contain material. Tubes may have variouslyshaped cross-sections (e.g., circular, oval, elliptical, polygonal,etc., or combinations thereof), and in some instances a tube may haveone or more openings in its sidewall. In various embodiments, a tube mayalso be filled with a material that provides low resistance to bending(e.g., a flexible material such as a soft plastic, metallic braid,spring, etc.). As shown in FIG. 3B, in an exemplary embodiment, thepassive, flexible tube 304 is an elongate, hollow structure having alongitudinal axis A and a diameter d. In various embodiments, asillustrated in FIGS. 3 and 3A, the tube 304 is at least a portion (e.g.,a segment) of a surgical device 300 designed to be inserted into apatient to perform minimally invasive surgery. Accordingly, in variousembodiments, with reference to FIG. 3B, the tube 304 has an outerdiameter d, ranging from about 2 mm to about 12 mm, such as, forexample, from about 2 mm to about 8 mm, or, for example, from about 2 mmto about 5 mm. The thickness t of the tube wall 322, in variousembodiments, ranges from about 0.07 mm to about 0.38 mm, for example,from about 0.12 mm to about 0.25 mm for a tube having an outer diameterof about 5 mm. Furthermore, in various embodiments wherein the tube 304is a segment of a serial link structure (i.e., comprising only a portionof the arm), the tube 304 has a length ranging from about 6 mm to about80 mm.

Those of ordinary skill in the art would understand, however, that thetube 304 may have various dimensions (e.g., diameters and/or lengths)and be formed from various resilient and biocompatible materialsincluding, for example, stainless steel, titanium, shape-memory alloys(e.g., various pseudoelastic/superelastic materials, such as nitinol),plastic or a composite, and that the dimensions and material used forthe tube 304 may be chosen as desired based on surgical application,strength, cost, and other such factors.

As illustrated in FIGS. 3A and 3B, the slits 321 in the wall 322 of thetube 304 are disposed along at least a portion of the length of the tube304, and are oriented generally transverse to the longitudinal axis A ofthe tube 304. In other words, each slit 321 lies within a plane that isgenerally transverse to the longitudinal axis A of the tube 304. Thoseof ordinary skill in the art would understand, however, that the slits321 may have various orientations with respect to the longitudinal axisA of the tube 304. In various embodiments, for example, each of theslits 321 may be oriented in planes angled from about 45 degrees toabout 90 degrees (i.e., perpendicular) relative to the longitudinal axisA of the tube 304. In an exemplary embodiment, the slits 321 are formedby laser cutting, and they extend through the thickness t of the tubewall 322. Depending on the material of tube 304, however, the slits 321may be formed using various techniques and/or methods as would beunderstood by those of ordinary skill in the art, including, forexample, using a slitting saw, water jet cutting, injection molding,and/or electric discharge machining (EDM). Furthermore, in variousembodiments (not shown), the slits 321 may extend partially through thethickness of the tube wall 322 (e.g., formed in an outer surface of thetube wall).

The tube 304 may comprise various slit configurations (e.g., patterns,numbers, arrangement relative to each other, and/or dimensions). Thoseof ordinary skill in the art would understand, for example, that themechanical properties of the tube 304 can be modified by changing theconfiguration. Consequently, depending on a particular surgicalapplication, those of ordinary skill in the art would understand how todetermine suitable slit patterns, numbers, arrangements, and dimensions,including, for example, slit width (as measured by the distance betweenopposing tube wall surfaces that define a slit), slit density (thenumber of slits 321 per unit length of tube 304), and the length of eachslit 321 (the distance between two ends of a slit 321 measured around aperiphery of the tube 304), to achieve desired tube properties (e.g.,flexibility and stiffness). In various exemplary embodiments, forexample, a tube 304 with an outer diameter of about 5 mm may have a slitwidth in the range of about 0.001 inches to about 0.010 inches, withspacing between each slit in the range of about 0.005 inches to about0.030 inches. Furthermore, by way of example, although FIG. 3A shows thetube 304 having slits 321 along substantially the entire length of thetube 304, the slits 321 could be formed only along a portion of the tubeor could be formed in discrete sections along the length of the tube304.

In various exemplary embodiments of the present teachings, the slits 321may be configured to provide various ranges of bending about thelongitudinal axis A of the tube 304 when the tube 304 is in the flexiblestate. In various embodiments, for example, the slits 321 provide arange of bending ranging from about 10 degrees to about 45 degrees. Invarious additional embodiments, the slits 321 provide a range of bendingof about 10 degrees per inch of length of the tube 304. Differingpatterns and arrangements of the slits 321 may also be used in differingregions along the length of the tube 304 to provide varying ranges ofbending or stiffness along a length of tube 304. In various embodiments,for example, the slits 321 may be configured to provide less flexibilityat the ends of the tube 304 (i.e., at locations where the passive,flexible tube 304 connects to joints 303 and 305) as compared to centralregions along the length of the tube 304 where greater flexibility maybe desired.

As shown in FIGS. 3A and 3B, to provide a substantially isotropic bendin the tube 304, in various embodiments, the slits 321 may follow ahelical path around the periphery of the tube 304 (e.g., the slits 321may comprise a helical pattern). In other words, the slits 321 are cutalong a line 360 that spirals around the tube 304. In one exemplaryembodiment, for example, the slits 321 are cut at a relatively finepitch of about 0.5 mm (turns per longitudinal length of tube 304). Insuch a configuration, each cut along the line is about 170 degrees ofthe tube circumference, followed by a non-cut length of about 30 degreesof the tube circumference. This cut pattern, for example, provides 40degrees of offset between the start point of each slit 321 (i.e.,between slit ends that are stacked adjacent one another as the patternmoves longitudinally along the tube 304). As illustrated in FIGS. 3A and3B, this cut pattern results in a double helix pattern of slits 321 anda double helix pattern of uncut lengths (e.g., solid, uncut wall regionsbetween slit ends) along the length of the tube 304. As shown withparticular reference to FIG. 3A, the line 361 depicted by the uncutregions illustrates one of the double helixes that spirals around thetube 304 (although at a relatively coarser pitch than the line 360 alongwhich the cuts are made). Although not wishing to be bound by aparticular theory, it appears that this spiral formed by line 361 ofuncut regions acts as a coil spring would act to support and stiffen theslitted tube 304. Thus, as would be understood by those of ordinaryskill in the art, various tube characteristics (e.g., longitudinalstiffness, plasticity, etc.) may be determined by the parameters of thespiral of uncut regions 361 (e.g., the pitch of the line 360 along whichthe cuts are made, the cut lengths along the line 360, and the uncutlengths along the line 361).

It can be seen that for certain slit patterns, the tube ends may rotatewith reference to one another as the tube is longitudinally compressedto place it in the stiffened state. And so, in various embodiments, forexample, to prevent twisting of the ends of the tube 304 relative toeach other during compression of the tube 304 (i.e., during thestiffened state), the slits 321 on a first length of the tube 304 mayfollow a right-hand helical path and the slits 321 on a second length ofthe tube 304 may follow a left-hand helical path (not shown).Alternatively, the slits may be patterned so that a known rotation ofone end of the tube with reference to the opposite end is obtained whenthe tube is compressed into the stiffened state.

To alter the tube 304 between a flexible state (see FIG. 5A) and astiffened state (see FIGS. 5C and 5D), one or more force transmissionelements can be coupled to the tube 304. As would be understood by thoseof ordinary skill in the art, a force transmission element may comprisea variety of tension elements, such as, for example, a cable, a wire, afilament, or a rod, and/or compression elements, such as, for example, apush rod. Suitable materials for the force transmission elements caninclude metals and polymers, for example. As would be further understoodby those of ordinary skill in the art, force transmission elements mayhave various configurations (e.g., numbers and/or locations), and thenumber and location of used may be chosen as desired based on surgicalapplication, efficiency, cost, and other such factors. The forcetransmission elements, whether tension or compression elements, havesufficient strength to transmit a force to the tube to stiffen and/orbend the tube as desired, but also are sufficiently flexible to permitbending of the force transmission element with the bending of the tube.The force transmission elements may be part of an actuation/tensioningsystem commonly used in various articulating minimally invasive surgicaldevices (e.g., arms, wrists, guide tubes). For example, the one or moreforce transmission elements can be part of the actuation mechanism 330used to control the overall surgical device 300 in the exemplaryembodiment of FIG. 3.

As shown in FIGS. 3 and 4, for example, in various embodiments, theforce transmission elements may comprise tension elements in the form ofa plurality of cables (two of which cables 331 and 332 are depicted inthe view of FIGS. 3 and 4, however those having ordinary skill in theart would understand that any number of cables may be used depending onthe desired application and movement of the surgical device) positionedwithin the tube 304. As shown in FIG. 3 and mentioned above, in variousembodiments, the cables 331 and 332 may comprise actuation cables thatare connected to and used to control (e.g., articulate and/or rigidize)segments of the serial link structure that are distal to the passiveflexible tube 304 (e.g., joint 305 and/or end effector 310) in theexemplary embodiment of FIGS. 3 and 3A.

As illustrated in the cut away view of FIG. 4 showing the interior ofthe tube, in various embodiments, cables 331 and 332 can be routedinternally through the lumen of the tube 304 to ultimately connect to anactuation mechanism at a proximal end of the surgical device and to oneor more segments of the surgical device distal to the tube 304, as shownby the extension of the cables 331 and 332 past the tube on the righthand side in the view of FIG. 4. In exemplary embodiments, it may bedesirable, though not necessary, to include routing members 341, shownschematically, to receive and position the cables 331 and 332 proximatean interior of the tube wall. Exemplary routing members are discussed inmore detail below with reference to the exemplary embodiment of FIG. 11.Routing members 340 can be used to keep the cables 331 and 332 away fromthe center of the lumen of the tube 304 so as to reduce the risk of thecables 331 and 332 interfering with other components (e.g., fibersensors, actuation members for controlling the end effector, and/orother instruments) that may be present in the lumen of the tube 304.

FIG. 4 also depicts exemplary end caps 342 that may be optionallyprovided on the ends of the tube 304 to use as a coupling structure toconnect the tube to other tubes or structures in a serial linkstructure. Although not shown in FIG. 4, the end caps 342 may beprovided with exterior surface features or other structures that canprovide a coupling to another structure in the serial link structure.

The passive, flexible tube 304 is placed in the flexible state byrelaxing cables 331 and 332. The tube 304 may be placed in the flexiblestate, for example, to navigate through a natural lumen to reach a worksite. As shown in FIG. 5B, in the flexible state, the tube 304 maypassively bend upon external forces acting thereon, such as, forexample, when the surgical device 300 encounters a wall of the lumenduring its navigation therethrough. In this manner, tissue damage may beminimized by allowing the tube 304, as well as potentially otherarticulable portions of the device 300, to passively bend upon a portionof the surgical device 300 impacting the lumen. As would be understoodby those of ordinary skill in the art, in various embodiments whereinthe cables 331 and 332 comprise actuation cables (e.g., to activelycontrol joint 305 and/or end effector 310), the passive, flexible tube304 may also passively bend via the movement of the other surgicalcomponents of device 300.

The pattern of slits 321 on the tube 304 may be thought of as creating aweb structure that when uncompressed allows the structure to bend intothe spaces within the web and when compressed prevents the structurefrom bending by closing the spaces within the web. FIG. 5A illustrates,for example, a diagrammatic view of the tube 304 in a flexible state. Asshown in FIG. 5A, the slits 321 are open, so that opposing surfaces 327and 328 defining a respective slit are apart. At the end of each slit321 is a web connecting element 350 (i.e., an uncut region of the tubewall). As also illustrated in FIG. 5A (as well as in FIGS. 3A, 3B, 5B,5C, and 10), the web connecting elements 350 are progressively offsetfrom one another by a small amount along the length of the tube 304 sothat they are arranged in a helical pattern in the tube 304. Thus,regions 352, as shown by the dashed line parallelogram shape, exist inthe tube 304 between the web connecting elements 350. Although notwishing to be bound by a particular theory, it appears that, as the tube304 bends, slight deformations occur in the web connecting elements 350(e.g., due to twisting of the connecting element.).

Accordingly, as would be understood by those of ordinary skill in theart, upon application of a bending moment (e.g., via an external force),the passive, flexible tube 304 may bend. In other words, as illustratedin FIG. 5B, at least some of the slits 321 on an outer bend radius 325of the tube 304 may open such that opposing slit surfaces 327 and 328are spaced apart from each other; while at least some of the slits 321on an inner bend radius 326 of the tube 304 constrict such that theopposing surfaces 327 and 328 defining those slits 321 are in contactwith, and in some cases pressed against, each other.

The passive, flexible tube 304 can be placed in the stiffened state byapplying tension T (see FIG. 4) to cables 331 and 332 (i.e., whereinboth T_(A) and T_(B) have the same tension T), which may be desirable,for example, once the end effector 310 is located at a work site. Asshown in FIGS. 5C and 5D, in the stiffened state, the tube 304 isstraightened and compressed along the longitudinal axis A. The stiffenedstate of the tube 304 can provide a stable base for operation of the endeffector 310 by preventing or substantially minimizing bending of thetube 304. As depicted in FIG. 5C, in the stiffened state, the tube 304is compressed along the longitudinal axis to constrict the slits 321 sothat opposing slit surfaces 327 and 328 contact each other, and, forexample, press against each other.

FIG. 5D illustrates a diagrammatic view of the tube 304 in a stiffenedstate. As shown in FIG. 5D, the tube 304 has been longitudinallycompressed, as illustrated by arrows 354 (force transmission elements,such as internal cables 331 and 332, are not shown). This longitudinalcompression brings opposing slit surfaces 327 and 328 against oneanother so that the slit is effectively closed. It can be seen that somelongitudinal shortening of tube 304 occurs as the slits 321 are closed.As described above, for the configuration shown, the web of slits alsotends to rotate (twist) around the tube's longitudinal axis duringcompression. Although not wishing to be bound by any particular theory,it appears that this rotation is caused by a small deformation in theregions 352, which results in the next distal-most web connectingelement 350 being further offset from each preceding web connectingelement 350, as illustrated by arrow 356 in FIG. 5D.

Those of ordinary skill in the art will understand, however, thatvarious patterns of slits 321, and hence various patterns of webconnecting elements 350 (i.e., uncut regions of the tube wall), may beused to provide various tube 304 bending and rigidizing features. Forexample, as described above, a helical pattern of connecting elements,at a particular slit density, may produce a known compression twistalong a particular tube length. Accordingly, two substantially equallength portions of the tube 304, with opposite helical patterns ofconnecting elements 350, will produce opposite twists that willeffectively offset one another so that there is no recognizable twistbetween opposite ends of the tube 304.

FIGS. 5E and 5F, for example, illustrate diagrammatic views of a tubeshowing slit/connecting element patterns in accordance with variousadditional embodiments of the present teachings. As shown in pattern5358 of FIG. 5E, the connecting elements 5350 are longitudinallyaligned. Accordingly, as would be understood by those of ordinary skillin the art, pattern 5358 induces a preferential bending in tube 5304, sothat tube 5304 bends to the left and to the right, but not into or outof the plane of the paper (opposite side connecting elements are hiddenbehind the ones shown). Further, maintaining a relatively small width ofconnecting elements 5350 relative to the diameter of the tube 5304 canfacilitate the ability to place the tube 5304 in a stiffened state. Asshown in pattern 6359 of FIG. 5F, each subsequent pair of connectingelements 6350 are offset from the preceding pair of connecting elements6350 by 90 degrees. Accordingly, as would be understood by those ofordinary skill in the art, pattern 6359 induces no preferential bendingdirection for the tube 6304, and there is effectively no longitudinaltwist when tube 6304 is compressed and stiffened. Furthermore, in thisembodiment, since the areas 6352 between the connecting elements 6350are relatively large, material stress within areas 6352 appears to beminimized during compression. As mentioned above, those of ordinaryskill in the art will also understand that various other patterns ofslits and connecting elements may be used with various slit densitiesand/or tube lengths to produce desired tube flexibility and stiffeningfeatures.

Although it is envisioned that a variety of cable actuation methods andtechniques known to those skilled in the art may be implemented to alterthe tube 304 between a flexible and stiffened state, various exemplaryembodiments in accordance with the present teachings may utilizeactuation methods and techniques such as disclosed, for example, in U.S.patent application Ser. No. 12/945,734 (filed Nov. 12, 2010; entitled“Tension Control in Actuation of Multi-Joint Medical Instruments”), U.S.patent application Ser. No. 12/494,797 (filed Jun. 30, 2009; entitled“Compliant Surgical Device”), and U.S. Patent Application PublicationNo. US 2010/0082041 A1 (filed Sep. 30, 2008; entitled “Passive Preloadand Capstan Drive for Surgical Instruments”), the entire contents ofeach of which are incorporated by reference herein.

As shown in the schematic representation of FIG. 3, for example, invarious embodiments, a surgical device 300 may further comprise anactuation mechanism 330 to actuate the one or more force transmissionelements, thereby altering the passive, flexible tube 304 betweenflexible and stiffened states. The actuation mechanism 330 is, forexample, a transmission mechanism that receives forces from an actuatorand transmits the forces to the device's distal components. Asillustrated in the schematic representation of FIG. 6, in variousexemplary embodiments, the actuation mechanism 330 acts as atransmission that converts torques applied by drive motors (i.e.,actuators) 342 and 344 into tensions in respective cables 331 and 332.As shown in FIG. 6, in various embodiments, the actuator comprises oneor more motors 342 and 344 that directly couple to capstans 343 and 345around which respective cables 331 and 332 wrap. The cables 331 and 332can therefore be actuated by respective motors 342 and 344 to compressthe tube 304 (e.g., to put the tube in a stiffened state). In variousadditional embodiments, the actuator is backdrivable to overcome a basepretension force in the cables 331 and 332. In other words, a baselinetension force in the cables 331 and 332, applied by respective passivepreload systems 346 and 347, may be sufficient to compress the tube 304(e.g., to put the tube in a stiffened state), and the cables 331 and 332can be actuated by backdriving the motors 343 and 344 to relax thecables 331 and 332, thereby placing the tube 304 in a flexible state.Reference is made to U.S. Application Publication No. US 2010/0082041 A1for various devices and methods for actuating the cables. Briefly, thetensioning element is a tendon. The surgical device uses a passivepreload system attached to the tendon, which is wrapped around acapstan. The passive preload system controls relaxed state tension inthe tendon. The passive preload system can employ a spring or otherstructure to apply tension to the tendon. The capstan can be driven by amotor when the tendon is needed to pull on a structural member of theinstrument (e.g., one or more of the instrument's distal endcomponents). For example, for an application of clamping pressure ormovement of the structural member against resistance, capstan frictionon the tendon can produce tendon tension that is many times the tensionapplied by the passive preload system. However, when the tendon is notneeded to apply force to the member, the capstan can be freed, so thatthe preload system provides enough tension to prevent tendon derailmentor other malfunctions. The low, preload tension in relaxed state tendonscan reduce overall tendon friction, particularly in instruments withflexible shafts that actuate only some tendons for desired controlinputs (e.g., distal end steering).

Although it is envisioned that a variety of control systems and methodsknown to those of ordinary skill in the art may be implemented toactuate the one or more force transmission elements (e.g., to alter thetube 304 between flexible and stiffened states), various exemplaryembodiments in accordance with the present teachings may utilize systemsand methods such as disclosed, for example, in U.S. patent applicationSer. No. 12/780,417 (filed May 14, 2010; entitled “Drive Force Controlin Medical Instruments Providing Position Measurements”), the entirecontents of which are incorporated by reference herein. As shown in FIG.6, for example, in various embodiments, a surgical device 300 mayfurther comprise a control system 355 to actuate cables 331 and 332. Itshould be further understood that a powered actuation system is notnecessarily required, and that in certain instances the necessaryactuation force may be, for example, a hand-operated lever, whichfunctions as the actuator for a force transmission element.

In various additional embodiments, a surgical device may implementsensing technology such as disclosed, for example, in U.S. patentapplication Ser. No. 12/490,487 (filed Jun. 24, 2009; entitled “Arm witha Combined Shape and Force Sensor”) and U.S. Pat. No. 7,720,322 B2(filed Jun. 30, 2008; entitled “Fiber Optic Shape Sensor”), the entirecontents of which are incorporated by reference herein, to measure theconfiguration of the tube. Accordingly, to control actuation of the atleast one force transmission element, various exemplary embodiments ofthe present teachings, may comprise a sensor configured to measure theposition and/or orientation of the tip (i.e., distal end) of the tube304 relative to the base (i.e., proximal end) of the tube 304 and acontrol system that receives position and/or orientation informationfrom the sensor.

As used herein, “configuration of a tube” or “configuration of asegment” refers to a general configuration of the tube or segment thatoccurs from having one or more bends in the tube or segment of a tube.For example, the configuration can refer to a measured position and/ororientation of the tip (i.e., distal end) of the tube or segmentrelative to the position and/or orientation of the base (i.e., proximalend) of the tube or segment. Those of ordinary skill in the art wouldtherefore understand that as used herein, the term configuration canrefer to one or more parameters that can be determined (e.g., measured)based on the three-dimensional geometric shape of the tube or segment;such parameters can include, but are not limited to, for example,position, orientation, velocity, acceleration etc.

As shown schematically, for example, in FIG. 3, a sensor, such as, forexample, an optical fiber 333 is routed through the instrument 300 sothat the distal end of fiber 333 terminates, for example, at or near thedistal end of segment 306. The position and orientation of the distalend of instrument 300 can be determined, for example, by a segment ofthe fiber 333 within segment 306. In various embodiments, actuation ofthe cables 331 and 332 may therefore be robotically controlled orcomputer-assisted using an existing control system and sensor 333implementing a feedback loop that monitors, for example, joint pairs303, 305, and segment 306. As those of ordinary skill in the art wouldunderstand, such a control scheme gives joints 303 and 305 an “activestiffness” dependent on the system's characteristics (e.g., actuationcable stiffness, lever arm, etc.) and control parameters (e.g., gains,etc.). Accordingly, as long as the tube 304 is stiffer than the feedbackcontrolled joints 303 and 305 (i.e., in the stiffened state), impact onan existing control system is minimal.

As above, those ordinarily skilled in the art would understand thatsurgical device 300 is exemplary only and not intended to be limiting ofthe present teachings and claims, but rather to illustrate one exemplaryconfiguration of a surgical device which may utilize the passive,flexible tubes in accordance with exemplary embodiments of the presentteachings. A surgical device may therefore comprise various types,numbers, and/or configurations of components depending upon theparticular surgical application desired.

In accordance with various additional exemplary embodiments of thepresent teachings, for example, as shown in FIG. 7, a surgical systemmay comprise a curved cannula 720 and a surgical device 700 with apassively flexible shaft that extends through the cannula 720. Thesurgical device 700 may comprise several passive, flexible segments,such as a passive, flexible tube 702 (e.g., which may be made of arelatively flexible material) and a passive, flexible tube 704 having aplurality of slits 721 on an exterior surface thereof. Surgical device700 includes, for example, a serial link structure comprising a seriesof segments 702, 704, and 706 interconnected by joints 703 and 705. Invarious embodiments, a surgical end effector 710 (e.g., grasper, needledriver, shears, cautery tool, camera, and the like) is coupled to thedistal end of segment 706. By way of example, therefore, a rigid link804 of a surgical device 800, as depicted in the embodiment of FIG. 8,can be replaced with the passive, flexible tube 704 to provide anarrangement that can offer increased flexibility to a shaft as itextends through a cannula. As would be understood by those of ordinaryskill in the art, such an application allows the surgical device 700 toextend through a rigid, curved cannula 720 having a relatively smallinner diameter and small bend radius (as compared with surgical device800, which may only navigate through rigid, curved cannula 820 having arelatively large inner diameter (i.e., relative to the outer diameter ofthe device 800) and/or large bend radius (see FIG. 8)). Thus, when asurgical device like surgical device 700 is used, the rigid, curvedcannula (or other entry guide) diameter may be made relatively smallerto minimize patient trauma. Reference is made to U.S. patent applicationSer. No. 12/618,608 for various types and configurations of cannulasystems suitable for application of the flexible tubes of the presentteachings.

Actively Controlled, Flexible Surgical Devices

In accordance with further aspects of the present teachings, one or moreslitted tubes, or segments of a slitted tube, may be actively controlledto bend in various ways. Thus, the slitted tube may be placed into astiffened state and into a passively flexible state, as described above,and still further into an actively controlled state in which the tube iscontrolled to achieve a desired shape.

As discussed above, to provide flexibility to a linked surgical device,a passive, flexible tube comprising slits may be used as a segmentbetween the device's articulated joints. To provide a stable base (e.g.,for operation of a surgical end effector of the surgical device), thepassive slitted tube may be compressed to straighten and stiffen thetube, for example, along with other segments (e.g., links) to which thetube is interconnected. In various other exemplary embodiments, however,rather than being used with a plurality of interconnected articulatedjoints (i.e., as a segment of an overall serial link structure), one ormore tubes comprising a plurality of slits may be used alone to providean active, continuously flexible, articulating arm that can replace aserial link structure (e.g., replace the link structure of FIG. 1). Aswith the passive tube embodiment, such an active, continuously flexibletube may be compressed to straighten and stiffen the tube by pressingthe slits' surfaces against each other, thereby creating a rigid armwhen desired.

FIG. 9, for example, illustrates a continuously flexible surgical device900 wherein a slitted tube 904 makes up the entire actively controlledportion of the device 900 (i.e., there are no other serial linkstructures used to provide the articulation to the device 900). Asillustrated, surgical device 900 includes an active, flexible tube 904having two active, continuously flexible articulating segments 906 and907 (e.g., a plurality of actively controlled articulating sections ofone continuously flexible tube 904). As shown in FIG. 9, in variousembodiments, a surgical end effector 910 (e.g., grasper, needle driver,shears, cautery tool, camera, and/or the like) is coupled to the distalend of tube 904, and the proximal end of the tube 904 is connected to abase tubular structure 905 to support the tube 904 and ultimatelyprovide a connection to an actuation mechanism 930. Although the basestructure 905 can exhibit some flexibility (e.g., be made of a somewhatflexible material), it is sufficiently rigid so as to passively bendminimally in response to movement of the segments 906, 907. Further basestructure 905 can be made of a material, or otherwise reinforced (e.g.,via sheaths as is described in further detail below), so that it issubstantially incompressible and able to withstand a compressive forceexerted by stiffening and/or bending of segments 906 or 907.

Those of ordinary skill in the art would understand that the active,flexible tube 904 may have various dimensions (e.g., diameters, wallthicknesses, and/or lengths) and be formed from various resilientmaterials including, for example, stainless steel, titanium, nitinol,plastic, or a composite, and that the dimensions and material used forthe tube 904 may be chosen as desired based on surgical application,strength, cost, and other such factors. In various embodiments, asillustrated in FIGS. 9, the active, flexible tube 904 comprises theentire arm of the surgical device 900. Accordingly, in variousembodiments, each segment 906 and 907 of the tube 904 has a lengthranging from about 3 to about 20 or more times the outer diameter of thetube 904. In various embodiments, each segment 906 and 907 has adifferent length. In various embodiments, for example, segment 906 is arelatively longer segment and segment 907 is a relatively shortersegment.

As shown in FIG. 10, and described in detail above with regard to FIGS.3A, 3B, and 5A-5E, the active flexible tube 904 has a plurality of slits921 in the tube wall 922. To alter the tube 904 between a flexible state(e.g., similar to that shown in FIGS. 5A and 5B) and a stiffened state(e.g., similar to that shown in FIGS. 5C and 5D), one or more forcetransmission elements can be coupled to the tube 904. As shown in thecross-sectional view of FIG. 11, for example, in various embodiments,the force transmission elements can comprise a plurality of tensionelements, such as, for example, cables positioned within the tube 904.In the view of FIG. 11, two cables 931 and 932 are depicted asrespectively corresponding to actively control the segments 907 and 906of the tube 904. Those having ordinary skill in the art will appreciatethat more than one cable may be associated with one or more of thesegments to achieve multiple DOF movement of the segment. For example,as shown in the cross-sectional views of the segments 906 and 907 inFIGS. 11B and 11C, respectively, in an exemplary embodiment each of thesegments 906 and 907 has three cables (931, 931′, 931″ corresponding tosegment 907; 932, 932′, and 932″ corresponding to segment 906)associated therewith to actively control the motion (e.g.,bending/stiffening) of the segments 906 and 907. Those ordinarilyskilled in the art would appreciate that the differing segments also mayhave a differing number of cables (e.g., ranging from one to more thanone, for example, from 1 to 4) associated therewith depending on theoverall movement of the tube 904 that may be desired.

As illustrated in FIGS. 11 and 11A-11C, in various embodiments, cables931 and 932 are routed along an interior wall of the tube 904 viarouting members 941. To maintain sufficient flexibility of the tube 904in the regions where routing members 941 are positioned to permitstiffening and/or bending of the tube 904, the routing members 941 canbe configured to permit both flexing and compressing of the tube 904.Suitable routing member structures may therefore include, but are notlimited to, a plurality of discrete rings, loops, hooks or other similarstructures, a laser cut hypotube (for example, cut to form a pluralityof rings disposed along the interior wall of the tube 904, as shown inFIG. 11), a coil spring attached at various points along its length tothe interior wall, or other similar structures that permit bending andcompression of the tube 904. The routing members may be attached to theinterior wall of the tube via welding, or other suitable bonding orsecuring mechanism. In the exemplary embodiment wherein the routingmembers comprise a laser cut hypotube, each of the plurality of slits921 can also extend through the hypotube. In other words, in variousembodiments, the tube wall 922 with attached hyptotubes 941 is laser cutin a desired pattern so that the tube/hypotube assembly substantiallybecomes a single, flexible piece. In various additional embodiments (notshown), one or more slitted hyptotubes can be attached to an exteriorsurface of the tube 904 (i.e., along the exterior of the tube wall 922).

The routing members 941 may be formed from various materials including,for example, stainless steel, nitinol, titanium, reinforced plastics,and/or composite materials. Those of ordinary skill in the art wouldunderstand how to select a material for the routing members 941 based onfactors such as, for example, application, flexibility, cost, etc. Forrouting members comprising hypotubes, suitable materials may include,for example, compressible plastics, such as, for example, expandedpolytetrafluoroethylene (PTFE). In one exemplary embodiment, routingmembers comprising discrete rings, loops, hooks and the like may be madeof wire or other filament structures that provide sufficient strength toroute the cables, but also allow the tube 904 to bend and compress.

In some exemplary embodiments, it also may be desirable to incorporatestructures with the flexible tube that decouple the behavior (e.g.,motion and/or stiffening) of a proximal segment and a distal segment. Inthis way, when an articulable distal segment is bent and/or stiffened bya force transmission element that also passes through one or moreproximal segments, the resulting force that is transmitted to a proximalsegment can be reduced. Likewise, structures that decouple the motionbetween proximal and distal segments can also reduce unintended motionof distal segments based on motion of one or more proximal segments. Inthe exemplary embodiment illustrated in FIGS. 11 and 11A-11C, the tube904 includes flexible, substantially incompressible sheaths 940 thatextend along an interior wall of the base structure 905 and segment 906of the tube 904. Cables that actively control a segment (e.g., 906and/or 907) can be routed through the sheaths 940. Thus, for example,the cables 931 that are actuated to actively bend or stiffen segment 907are routed through sheaths 940 in base structure 905 and in segment 906,and the cables 932 that are actuated to actively control segment 906 arerouted through sheaths 940 in base structure 905. The sheaths 940 areseparated from the interior wall of the tube 904 and tubular basestructure 905, and are attached (e.g., welded, bonded, or otherwisesecured) thereto at their distal ends via end caps 942. Consequently,the sheaths 940 can carry the compressive load that is exerted byactuation of the cables 931, 932 to control (e.g., bend or stiffen) amore distal flexible segment. By routing the cables 931 and 932 throughthe substantially incompressible sheaths 940, the actuation of thecables 931 and 932 will not transmit substantial force to the basestructure 905 and the segment 906 of tube 904 to which the sheaths 940are attached, as the sheaths 940 will tend to carry that force instead.This can avoid, for example, undesirable stiffening of the segment 906due to the compressive loading from the actuation of cables 931 and 932.

In various exemplary embodiments, the sheaths 940 can comprise a coiltube, a partially laser cut hypotube (e.g., sufficient to provideflexibility in bending yet remain substantially incompressible), ahelical hollow strand bundle of relatively stiff wire, a plastic tube,and other structures that are flexible but sufficiently incompressibleso as to achieve decoupling of the transmission of the force from forcetransmission elements, such as, for example, cables 931 and 932, routedtherethrough. As shown in FIG. 11, routing members 941 may be disposedto receive the cables 931 and 932 once they emerge from the sheaths 940into segments that are actively controlled by the respective cables.

In use, the active, flexible tube 904 is placed in the flexible, bendingstate by actively applying a tension (e.g., indicated as T_(A) and T_(B)in FIG. 11) to selected cables 931, 931′, 931″, 932, 932′, and/or 932″(e.g., as the surgical device 900 is navigated through a natural lumen).As illustrated in FIG. 11, applying a tension T_(A) on cable 931 willcause segment 907 to bend in a counterclockwise direction (as viewed),while applying a tension T_(B) on cable 932 will cause segment 906 tobend in a clockwise direction (as viewed). As would be understood bythose of ordinary skill in the art, upon application of a bending moment(e.g., via an internal cable such as 931, 931′, 931″, 932, 932′, and/or932″), the tube 904 will bend until it reaches a stop. In other words,as illustrated in FIG. 5B with regard to slits 321, at least some of theslits 921 on an outer bend radius of the tube 904 may open such thatopposing surfaces defining a respective slit are spaced apart from eachother. In various embodiments, for example, upon maximum bending of thetube 904, the slits 921 on an outer bend radius of the tube 904 may opensuch that opposing surfaces defining a respective slit are spaced apartfrom each other about twice as much as when the tube 904 is in a relaxed(i.e., unbent or passively flexible) state. In this manner, the tube 904may bend until the slits 921 on an inner bend radius of the tube 904 arefully constricted such that the opposing surfaces defining those slits921 are in contact with, and in some cases pressed against, each other.

As would be understood by those of ordinary skill in the art, in variousadditional embodiments, to further bend the tube 904 after it reaches astop at which the opposing surfaces defining the slits contact eachother, an additional active force may be applied to the tube using acompression member that can apply a force sufficient to further expandand space apart the opposing surfaces of the slits on the outer bendradius of the tube, while causing the opposing surfaces of the slits onthe inner bend radius of the tube to pivot about each other at an innermost contact edge. FIG. 14A shows a cross-sectional view of an exemplaryembodiment of an active flexible tube 1904 or segment thereof thatincludes flexible rods 1935 and 1936 (e.g., which can act as push rodsor pull rods as described below) for controlling the bending of the tube1904. As with the tension elements described above, the rods 1935 and1936 can be first received through sheaths 1940 and then through routingmembers 1941, such as the various sheaths and routing members that havebeen described herein. To bend the tube 1904 in a clockwise direction(as viewed), a tension force T_(P) can be applied to the rod 1936, whichcan cause the tube 1904 to bend until the opposing surfaces defining theslits 1921 on the inner bend radius of the tube 1904 press against eachother (e.g., as described with reference to FIG. 5B). To further bendthe tube 1904 past the stop limit associated with pulling the rod 1936,a compressive force C_(P) can be applied to the push rod 1935 along theouter bend radius of the tube 1904. This may further bend the tube 1904such that the spacing between the opposing surfaces of the slits 1921 onan outer bend radius of the tube gets larger than the spacing thatoccurs as a result of pulling on rod 1936 alone (e.g., larger than thatin FIG. 5B). In addition, the further bending also can result in theopposing surfaces of the slits 1921 on an inner bend radius 1926 of thetube pivoting relative to each other about an innermost contact edge.For example, as depicted in the schematic representations of FIG. 14Band 14C of a slit 1921 on an inner bend radius I of the tube 1904, theopposing surfaces 1927, 1928 defining the slit 1921 are in contact witheach other as a result of actuation of the tension element 1930, asshown in FIG. 14B. Further bending of the tube via a compression element(e.g., pushing on rod 1935) causes the opposing surfaces 1927, 1928 ofthe slit 1921 to pivot about an innermost contact edge upon actuation ofthe push rod 1935, as depicted in the schematic representation of FIG.14C, thereby creating an opening between the opposing surfaces 1927,1928 on the inner bend radius 1926 at least along an interior of thewall of the tube.

In various exemplary embodiments, the rods 1935, 1936, or othercompression elements, are sufficiently rigid to withstand a compressiveforce that can be transmitted to the flexible, tube, yet sufficientlyflexible to permit bending of the compression element with the bendingof the tube. Also, although the exemplary embodiment of FIG. 14Aillustrates compression elements (rods 1935, 1936) disposed along aninterior of the tube 904, one or more compression elements could bedisposed along an exterior of the tube. Further compression elements andtension elements may be used in combination in various exemplaryembodiments to control the bending/stiffening of the tube.

With reference again to FIG. 11, the active, flexible tube 904 is placedin the stiffened state by applying tension T (i.e., wherein T_(A) andT_(B) have the same tension T) to all of the actuation cables 931, 931′,931″, 932, 932′, 932″ (e.g., once the end effector 910 is located at awork site). As above, in the stiffened state, the tube 904 is compressedalong the longitudinal axis to constrict the slits 921 so that opposingslit surfaces contact each other, and, for example, press against eachother (e.g., in a manner similar to that shown in FIGS. 5C and 5D).Accordingly, the stiffened state of the tube 904 can provide a stablebase for operation of the end effector 910 by preventing orsubstantially minimizing bending of the tube 904.

As shown in the schematic representation of FIG. 9, in variousembodiments, a surgical device may further comprise an actuationmechanism 930 to actuate the one or more force transmission elements(e.g., cables in the embodiment of FIGS. 9 and 11), thereby altering theactive, flexible tube 904 between flexible and stiffened states. Invarious exemplary embodiments, the actuation mechanism 930 acts as atransmission that converts torques applied by drive motors (i.e.,actuators) into forces in respective cables such as cables 931, 931′,931″, 932, 932′, and 932″. In various embodiments, for example, theactuation mechanism 930 can be the same as the actuation mechanism 330described above for FIG. 6. Accordingly, details of the actuationmechanism 930 are not reiterated here. In various additionalembodiments, the surgical device 900 may include a sensor, such as, forexample, an optical fiber 933. As shown in FIG. 9, fiber 933 may berouted through the instrument 900 so that fiber 933′s distal endterminates, for example, at or near the distal end of the tube 904.Accordingly, the configuration of each segment 906 and 907 can bedetermined, for example, by sensing the relative position and/ororientation of a tip portion (i.e., distal end) relative to a baseportion (i.e., proximal end) of a fiber segment within each segment 906and 907. Those of ordinary skill in the art would understand, however,that surgical device 900 is exemplary only and not intended to limit thepresent teachings and claims. Accordingly, aspects of the presentteachings can be embodied in various surgical devices and/orinstruments, such as, for example, cannula systems and guide tubes forother surgical instruments, as well as for tissue manipulatinginstruments themselves. Furthermore, in various embodiments, tube 904may comprise various types (i.e., passive and active), numbers, and/orconfigurations of continuously flexible bending segments like 906 and907 depending on the surgical application employed. For example, invarious embodiments, segments 906 and 907 are each actively flexed byone or more (e.g., three in the exemplary embodiment described above)cables respectively. In another exemplary embodiment, the flexible tubecould have three separately controlled segments with the most proximaland distal segments being active, flexible segments via one or moreforce transmission elements (e.g., three cables each to provide threeDOF movement), and a middle segment being a passive, flexible segment.In an exemplary embodiment, the passively flexible segment may include asingle, tension element along a centerline thereof to place it in astiffened state if desired. The preceding descriptions of the numbersand types of segments of a slitted flexible tube are exemplary only andnot intended to limit the scope of the present teachings or claims;various additional embodiments are contemplated and those havingordinary skill in the art would understand how to make modificationsbased on the teachings herein in order to provide a surgical devicesuitable to a desired application. Moreover, as those of ordinary skillin the art would understand, an actively flexible segment, when notactuated by its associated sources of force, can be passively flexible.

In various additional exemplary embodiments, the disclosure relates tomethods for altering a surgical device comprising a slitted flexibletube between stiffened and flexible states as described herein. FIG. 12,for example, shows a logic flow diagram depicting an exemplary methodfor a surgical device having the basic structure of device 900 of FIG.9. As shown at step 400 of FIG. 12, a command is received, for example,from a control system (e.g., 355, FIG. 6), to place a surgicalinstrument tube (e.g., tube 904) in a stiffened state. At step 402, thetube is longitudinally compressed. As discussed above with reference toFIGS. 5C and 5D, longitudinally compressing the tube causes opposingsurfaces of slits (e.g., slits 921) in the tube to contact one another,thereby preventing or substantially minimizing bending of the tube.

As shown at step 404 of FIG. 12, a command is then received to place thetube in a flexible state, and the tube is relaxed (i.e., thelongitudinal compression on the tube is reduced), as indicated by thelast step, 406. As discussed above with reference to FIGS. 5A and 5B,reducing the longitudinal compression on the tube allows the opposingsurfaces of the slits to separate from one another, thereby permittingthe tube to bend. In the flexible state, for example, the tube maypassively bend upon external forces acting thereon, such as, forexample, when the surgical instrument tube encounters a wall of thelumen and/or may actively bend upon actuation of one or more forcetransmission elements associated with the tube.

In various embodiments, to alter the tube between the stiffened andflexible states, the method may further comprise transmitting anactuation input to one or more force transmission elements associatedwith the tube, as described herein. In various embodiments, transmittingan actuation input to a force transmission element may comprisetransmitting the actuation input to a plurality of cables (e.g., cables931, 931′, 931″. 932, 932′, and/or 932″) associated with the tube. Asdiscussed above with reference to FIG. 6, for example, in variousembodiments, the tube may be longitudinally compressed by actuating thecables to provide a base pretension force; and the tube may be relaxed(i.e., the longitudinal compression on the tube may be reduced) byback-driving the cables to overcome the base pretension force. In anexemplary embodiment, an actuation mechanism such as that shown in FIG.6 may be used to actuate the one or more force transmission elements.

In various additional embodiments, as illustrated in FIG. 13, the methodmay further utilize shape sensing technology to actively control thebending of the tube. As shown, for example, at step 500 of FIG. 13, oncea command to place the tube in a flexible state is received, theconfiguration of the tube can be measured, such as by measuring positionand/or orientation of the tip (i.e., distal end) relative to the base(i.e., proximal end) of the tube. At step 502, a command that indicatesthe desired configuration of the tube (e.g., for a location at which aforce transmission element is anchored) can be received, for example viaa controller. At step 504, the controller can then determine anactuation input necessary to bend the tube from the measuredconfiguration to the desired configuration, and that input can betransmitted to a force transmission element associated with the tube, asindicated by the last step, 506 of FIG. 13. As discussed above, asurgical device may implement various shape sensing technologies asdisclosed, for example, in U.S. patent application Ser. No. 12/490,487and U.S. Pat. No. 7,720,322 B2, the entire contents of which areincorporated by reference herein. It is, therefore, within the abilityof one skilled in the art to select an appropriate method and controlsystem for sensing and controlling the configuration of the tube,including for example, interrogating a sensor to generateposition/orientation information about the tube and then, based on thatinformation, controlling an actuator to control a force (e.g., tensionor compression) on force transmission elements to thereby relax and/orstiffen the tube as desired in the manner explained above and as wouldbe understood by those having ordinary skill in the art in light of thepresent teachings.

Although various exemplary embodiments shown and described herein relateto surgical devices comprising either passive, flexible tubesinterconnected by joints, or active, continuously flexible tubes thatcan be used alone to replace a bendable serial link structure, thosehaving ordinary skill in the art would understand that the slitted tubesdescribed herein may have a broad range of application. In variousembodiments, for example, as would be understood by those of ordinaryskill in the art, tension elements may be attached to a flexible tube ina serial link structure such that tension on the tension elements mayact directly on the tube (i.e., to actively bend the tube uponactivation of one or more tension elements). In various additionalembodiments, continuously flexible tubes (e.g., used to replace a seriallink structure) can be modulated between active and passive states. Asthose of ordinary skill in the art would understand, for example, anactively flexible tube, when not actuated by its associated internallyoriginating sources of force, may be passively flexible. Accordingly, invarious embodiments, a surgical device may be configured (e.g., via acontrol system) to modulate between active and passive states by turningcable activation forces on and off

Furthermore, although various exemplary embodiments shown and describedherein relate to surgical devices used for minimally invasiveprocedures, those having ordinary skill in the art would understand thatthe structures and methods described may have a broad range ofapplication to surgical devices, robotic and non-robotic, useful in avariety of applications for which both flexibility and rigidity aredesired. Those having ordinary skill in the art would understand how tomodify the exemplary embodiments described herein to provide surgicaldevices that can be varied between flexible and stiffened states formany types of surgical procedures.

1. A surgical device comprising: a tube comprising a wall having aplurality of slits oriented generally transverse to a longitudinal axisof the tube, wherein each slit is defined by opposing surfaces; and aforce transmission element coupled to the tube; wherein in a flexiblestate of the tube, at least some of the opposing surfaces definingrespective slits are separated from one another; and wherein in astiffened state of the tube, a force exerted on the force transmissionelement causes the opposing surfaces of each slit to contact oneanother.
 2. The device of claim 1, further comprising an actuatorcoupled to the force transmission element.
 3. The device of claim 2,further comprising: a sensor that senses information regarding aconfiguration of the tube; and a control system that receives theconfiguration information from the sensor.
 4. The device of claim 3,wherein the sensor comprises an optical fiber sensor.
 5. The device ofclaim 2, wherein the actuator comprises a motor.
 6. The device of claim2, wherein the actuator is backdrivable to overcome a base pretensionforce in the force transmission element.
 7. The device of claim 1,wherein the tube is actively controlled to bend the tube.
 8. The deviceof claim 1, wherein the tube is a passive flexible segment of a seriallink structure.
 9. The device of claim 8, further comprising a jointcoupled to an end of the tube.
 10. The device of claim 1, wherein thetube is at least a portion of a surgical device configured for minimallyinvasive surgery.
 11. The device of claim 1, wherein the tube has anouter diameter ranging from about 2 mm to about 12 mm.
 12. The device ofclaim 1, wherein the tube has an outer diameter ranging from about 2 mmto about 8 mm.
 13. The device of claim 1, wherein the tube comprises astainless steel or a shape memory alloy.
 14. The device of claim 1,wherein the slits comprise laser cuts.
 15. The device of claim 1,wherein the slits provide a range of bending about the longitudinal axisof the tube from about 10 degrees to about 45 degrees.
 16. The device ofclaim 1, wherein the slits provide a range of bending about thelongitudinal axis of the tube of about 10 degrees per inch of the tube.17. The device of claim 1, wherein the tube bends substantiallyisotropically.
 18. The device of claim 1, wherein uncut regions of thetube wall that connect slit ends follow a helical path around aperiphery of the tube.
 19. The device of claim 18, wherein the uncutregions on a first length of the tube follow a right-hand helical pathand the uncut regions on a second length of the tube follow a left-handhelical path.
 20. The device of claim 1, wherein the force transmissionelement is positioned within the tube.
 21. The device of claim 1,wherein the force transmission element comprises a tension element. 22.The device of claim 21, wherein the tension element comprises a metal orpolymer.
 23. The device of claim 21, wherein the tension elementcomprises a cable.
 24. The device of claim 1, further comprising arouting member configured to receive the force transmission elementalong a length of the tube, wherein at least a portion of the slitsextend through the routing member.
 25. The device of claim 1, furthercomprising a sheath configured to receive the force transmission elementalong a length of the tube.
 26. The device of claim 25, wherein thesheath comprises a hypotube.
 27. The device of claim 1, wherein theforce transmission element comprises a rod.
 28. A method comprising:longitudinally compressing a surgical instrument tube when a command toplace the tube in a stiffened state is received, wherein longitudinallycompressing the surgical instrument tube comprises causing opposingsurfaces of slits in the tube to contact one another; and reducing thelongitudinal compression on the surgical instrument tube when a commandto place the tube in a flexible state is received, wherein reducing thelongitudinal compression on the surgical instrument tube comprisesallowing the opposing surfaces of at least some of the slits to beseparated from one another.
 29. The method of claim 28 furthercomprising, after the command to place the tube in a flexible state isreceived: measuring a configuration of the tube; receiving a commandthat indicates a desired configuration of the tube; determining anactuation input necessary to move the tube from the measuredconfiguration to the desired configuration; and transmitting theactuation input to a force transmission element associated with thetube.
 30. The method of claim 29, wherein measuring a configuration ofthe tube comprises interrogating a sensor that measures position and/ororientation information about the tube.
 31. The method of claim 28,further comprising, after a command to place the tube in a stiffenedstate or a flexible state is received: transmitting an actuation inputto a force transmission element associated with the tube.
 32. The methodof claim 31, wherein transmitting an actuation input to a forcetransmission element comprises transmitting the actuation input to acable.
 33. The method of claim 31, wherein longitudinally compressing asurgical instrument tube comprises actuating the force transmissionelement to provide a base pretension force.
 34. The method of claim 33,wherein reducing the longitudinal compression on the surgical instrumenttube comprises back-driving the force transmission element to overcomethe base pretension force.